In general, paints are very widely used in homes including kitchens, living rooms, etc. as well as all sorts of industrial fields including railroads, vehicles, ships, road facilities, electronics, electricity, etc.
However, the conventional organic paints using organic solvents, such as alcohol, etc., have the problem of environmental contamination. In the case where organic substances (for example, all kinds of oils, lacquer sprays, oil markers, etc.) stain and pollute the surfaces of conventional organic paints, it is not easy to remove the stain since the surfaces faces of organic paints are hydrophilic and thus combine easily with the organic substances.
Furthermore, organic paints have weak adhesive properties and adherence to adhere to the surfaces of metals and nonferrous metals. To coat organic paints on the surfaces of the metals and nonferrous metals, additional processes are required, such as pretreatments of sanding or acidizing the surfaces thereof or coating the surfaces thereof with a special substance having high adhesion. The coating processes are complicated and costs increase. In addition, if the service life is long or an external impact is applied, organic paints often peel away from the basic materials.
Organic paints also have the problems of being weak at a high temperature and being easily combustible. So, paints and coating agents to replace such organic paints have been continuously demanded.
To solve the aforementioned problems, an inorganic coating composition has been developed by using water soluble silicate and aluminum or using water soluble silicate prepared by aluminum metallic oxide as the main ingredients. However, since the water soluble modified silicate used as a binder in this inorganic coating composition is a strong alkali substance, after a coating film is formed, a small amount of an alkali element leaches out to the surface of the coating film, causing efflorescence.
A study has been also made on a hydrophilic inorganic paint composition having alkali metallic oxide and alkali silicate as a curing agent and metallic oxide, metallic phosphate and alkali silicate as a base. However, efflorescence caused by alkali leaching has not been completely prevented in this case. Further, water-proofing is not perfect and the adhesion or adherence to the basic materials needs to be improved.